1 Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, United States.
2 Department of Biomedical Engineering, Medical College of Wisconsin Graduate School of Biomedical Sciences and Marquette University, Milwaukee, WI, United States.
3 Department of Neurosurgery, University of California, San Francisco, San Francisco, CA, United States.
4 Department of Neurology, Mayo Clinic, Rochester, MI, United States.